Oh, Wisest ones:

I have a parent thread who forks a child which executes a script with exec, after a time, it kills such child (using the pid of the child forked)

This works wonderfuly

my $pidChild;
my $pid0=fork();
if ($pid0) {
  #parent process
  $pidChild=$pid0;
  print "Parent has launched child $pid0\n";
  sleep(10);
  my $killed=kill 'KILL', $pidChild;
  if ($killed) {
    print "Parent has killed child $pid0\n";
    }
  sleep(5);
  my @alive=`ps aux | grep process | grep -v grep`;
  print "@alive\n";
  }
else {
  #child 
  print "This is child $$\n";
  my $command='sh /path/process.sh';  
  exec($command);
  }

[download]

until I try to redirect the output of the executed script, then the pid changes.

my $pidChild;
my $pid0=fork();
if ($pid0) {
  #parent process
  $pidChild=$pid0;
  print "Parent has launched child $pid0\n";
  sleep(10);
  my $killed=kill 'KILL', $pidChild;
  if ($killed) {
    print "Parent has killed child $pid0\n";
    }
  sleep(5);
  my @alive=`ps aux | grep process | grep -v grep`;
  print "@alive\n";
  }
else {
  #child 
  print "This is child $$\n";
  my $command='sh /path/process.sh 2>&1';  
  exec($command);
  }

[download]

Also fails if I try to redirect the output to a file 

my $command='sh /path/process.sh > /pathlogs/mylog.log';

[download]

Why the redirection changes the pid? Are the script I am trying to execute and the redirection of its output different processes? What is it happening inside there?

Thank you a lot in advance for clarifying this mistery...

In reply to fork, exec and pid by luxAeterna

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